A support for a recording material produced by performing melt extrusion coating of thermoplastic resin on at least one side of a support such as base paper has been used by applying a photographic emulsion, a heat-sensitive material, and the like to the support. In the support for a recording material, the smoothness of a surface of the support prior to the application of the emulsion and the like has been known to be significant for obtaining a high-quality image. It is common that a method for producing the support for a recording material is a method in which thermoplastic resin melted at high temperature by an extrusion coating method is cast on a surface of transporting base paper, and nipped and coated between a press roller coated with elastomeric resin and a cooling roller via the base paper.
A method of setting the nip pressure, a method of increasing the thickness of a thermoplastic resin layer, a method of increasing the nip pressure during coating of thermoplastic resin, calender treatment for enhancing the smoothness of base paper, or the like has been known as a method for improving the smoothness of a surface of a support produced by melt-coating. However, the method of nipping a support and a resin is affected by the surface geometry of the support, the method of increasing the thickness of the resin is disadvantageous in view of a cost, and the calender treatment method results in the increased number of facilities and steps and is disadvantageous in view of a cost. None of the methods result in smoothness that can be sufficiently satisfied.
In order to solve such problems, there is proposed a method for producing a support for a recording material obtained by coating at least one side of a support such as base paper with thermoplastic resin extruded by a melt extrusion coating method, wherein the resin and the support such as base paper are passed through a gap set to have a distance of not less than the thickness of the support to be coated and less than the thickness of the coated support between a cooling roller and a press roller in a pair, and the support is coated (see Patent Literature 1).
However, a method for producing a support for a recording material having surface smoothness providing excellent texture in lamination of a substrate as a support and a porous film has not been conventionally known.